The present invention relates to a printing apparatus including tab position placement control for printing characters, symbols and numerals and, more particularly, to a printing apparatus with which input data can be efficiently corrected.
To prepare a table of numbers by using printing apparatuses, e.g., typewriters or word processors, the decimal points of numbers or the rightmost positions of numbers having no decimal points must sometimes be aligned.
For example, to print decimal number "123.456" by using a conventional manual or electrical typewriter, the typist sets a tab position where the decimal point should be printed. He or she then depresses the tab key, whereby the print head is moved to the tab position. The typist pushes the back-space key three times, returning the print head for a three-character distance. Then, he or she depresses the "1", "2", "3", ".", "4", "5", and "6" keys in this order, thus printing the decimal number with the decimal point printed at the tab position.
Electronic typewriters which have a memory, can store a document and can process the stored document, have recently become popular. Some of them are equipped with a so-called decimal tab key, "DEC TAB". To print decimal number "123.567" with the decimal point at a desired tab position, the typist first sets the desired tab position. He or she then pushes the "DEC TAB" key and depresses the "1", "2", "3", ".", "4", "5" and "6" keys. When the period key, "." is pushed, the data representing "123." is stored in the memory in such a manner that the decimal point will be printed in the tab position. When the return key, "RET", is finally depressed, the typewriter prints "123.456," with the decimal point at the tab position. To print the whole number "123", the typist depresses the "DEC TAB", "1", "2" and "3" keys, and the space key, "SPC". When the space key "SPC" is pushed, the data representing "123-" is stored in the memory in such a manner that the space will be located in the tab position. (Symbol "-" indicates a space.) When the return key, "RET", is depressed, the typewriter prints the whole number, with the space located at the tab position.
The electronic typewriters described in the preceding paragraph have a drawback. Let us assume that the typist has set the tab position at the tenth printing position and has mistakenly depressed the "1", "2" and "." keys after depressing the "DEC TAB" key, intending to print "123." In this case, the data stored in the memory is, "- - - 12." The typist must depress the cursor key, ".rarw." ten times and then depress the "1", "2", "3" and "." keys, in order to change this incorrect data to the correct data, "- - - 123." This cumbersome operation is required since, the cursor moves to the selected tab position when the "." key or "SPC" key is depressed after the "DEC TAB" key has been depressed.